Because of the attack of evil spirits, many believers lose their original power of memory and often have the phenomenon of forgetfulness. Words just spoken are forgotten in an instant, work just done is forgotten in an hour, things just put down are forgotten before the day is over, and things just promised are forgotten in a moment. The believer acts like a man without a mind; nothing seems to be retained in his mind. He may think that this happens because his memory is worse than someone else’s memory. Little does he realize that this is due to the disturbance of evil spirits in his mind. In such a condition, the believer finds himself jotting down all kinds of "memos," and becomes a slave to his notebooks. He must depend on these things as his "reminders"; otherwise, he will encounter difficulties all the time. We are not saying that a believer’s mind should remember all kinds of things. We admit that many things are forgotten through the passing of years, and even current events can be forgotten because the impression produced in the mind is not deep. We are not saying that believers should remember everything. However, other than the above-mentioned matters, there are many things which have not transpired long ago, which the believers have paid attention to. Given the short period of time and the circumstances, a believer should remember these things. Yet there is often not even a shadow of memory; he cannot recall anything. This is not natural; rather, it must be the attack of evil spirits. For example, it is not natural to forget what we have most recently paid attention to. Some forgetfulness is natural; some is not natural. Behind all the unnatural forgetfulness, there are the attacks of evil spirits. Evil spirits are very capable at taking hold of certain of our nerves at critical hours and making us forget what we should have remembered. Countless numbers of believers have suffered considerable hardships as a result of the attacks of evil spirits in this area. Many works are damaged because of this. Many embarrassments result from this. Therefore, the trust that others have in this type of person decreases, and his usefulness also decreases. Yet he still does not realize that these memory lapses are caused by the work of evil spirits in his mind.
At other times, a believer’s memory seems to be very good and does not seem to suffer from any sickness. But strangely, there are certain sudden lapses in his memory! At many critical junctures, when the mind should be working very well, it suddenly becomes muddled and cannot remember anything. As a result, matters fall into a hopeless situation. This sudden lapse in the function of the mind may seem strange to the believer. He may think that he is momentarily failing in his mental power and that this will last only for a little while; he does not realize that this is a phenomenon of the attack of evil spirits on the mind.
(Spiritual Man, The (3 volume set), Chapter 32, by Watchman Nee)